Process of making ferro-alloys and of making alloy steels from such alloys



UNlTED STATES PATENT FFEGE PROCESS OF MAKING FERRO-ALLOYS AND OF MAUNG ALLOY STEELS FROM SUCH ALLOY Ben F. Hardesty, Cleveland, .Ohio, assignor to Perfection Steel Company, Pittsburgh, Pa.

No Drawing. Application January 14, 1932, Serial No. 586,699. Renewed January 13,

8 Claims. 75-54) REISSUED purity and homogeneity. salt the following reactions are believed to take 5 The production of many alloy steels is, accord- Place: ing to the present practice, effected by introduc- When barium carbonate is heated to temperaing into the ferrous bath the ferro-alloys of the tures within those prevailing in a ferrous metal alloying metals such as chromium, molybdenum, bath, carbon dioxide is liberated with the formamanganese, tungsten, and others. Many of these tion, first, of the compound BaO, ZBaCOa, and 10 ferro-alloys are produced by the reduction of the h n, pon further loss of carbon dioxide, the ore concentrates of the alloying metal in the eleccompound 2BaO,BaCO3 is formed which does not tric furnace in the presence of carbon. The fery eld t e q a ities of CO2. Both comro-alloys so produced, however, are not definite pounds BaO, 2BaCO3 and 2BAO, BaCOs are highhomogeneous compounds but rather are hetero- 1y fusible and basic and react with the ferrous 15 geneous in character and contain undissociable and non-ferrous impurities to produce agglomercarbides, unreduced oxides and gangue products. ated compounds of l w m tin point which a Moreover, many of these carbides have higher therefore readily removable. melting points than the temperature of. the fer- For many purposes it may be desirable to add rous bath to which they are added. In such to the bath a mixture of the peroxide and the 20 cases, these carbides when introduced into the carbonate since the melting point of the mixture ferrous metal remain undecomposed and are segis somewhat lower than that of the components regated in areas in the finished steel and thereby and the basic carbonates formed act as a flux for constitute a serious detriment thereto. the barium monoxide formed of the peroxide 20 A most important application of my invention added.

is to steels containing chromium, particularly As a preferred example of a mixture which chrome nickel alloy steels, usually designated may be employed, but without limiting the instainless steels and containing roughly 20% vention thereto, I give the following: chromium and 10% nickel. At present the pro- Parts duction of stainless steels entails special diflicul- Barium peroxide 150 30 ties. which are reflected in the present high cost. Barium carbonate 50 Stainless e Particularly the rolled and A specific example of the process employed drawn varieties. As ordinarly produced, stainusing t above mixture is as fofl s; less steel contains sufiicient impurities, chiefly To the molten t of ferro chromium, as, for

,the carbides mentioned, unreduced oxides and example an alloy containing approximately 75% 35 probably nitrides, as to account for these diffichromium, 25 iron, 12 t 30% carbon, 1 add culties in the cold working of the metal. By refro twenty to forty pounds f t mixture of ducing the impurities, my invention makes P barium peroxide and barium carbonate above sible the production of stainless rolled sheet steel given per ton of meta], it being understood t 40 at greatly reduced cost- Moreover, on account this quantity of the mixture is susceptible to a 40 f the purity d re in du til y of the metal fairly wide variation. After the metal becomes it may, in many instances, be sub-lected to both quiet, it is ready to be added to the metal to be hot and cold Working Withmlt the necessity alloyed. Previous to thisthe bath of carbon steel annealingis prepared as by melting sheet and bar scrap,

The invention consists inthe treatment of the d adding thereto from twenty to forty pounds 45 metal bath with barium COmPOImd 0f the p of the above mentioned barium mixture per ton liberating xy he a ium pound most ofmetal, this having the same eflect of clearing P red by me is the peroxide since the barium the carbon steel bath of impurities. I then inmonoxide component thereof energetically forms troduce into the bath the purified ferrochrome 5 with the impurities of the bath low melting point alloy, and after sufficient time has elapsed for and low viscosity slags, whereas the excess oxythe ingredients to become mixed the bath is then gen component furnishes available oxygen to oxipreferably treated again with the barium perdize certain of the impurities and thus cause oxide mixture in order to eliminate any imthem to readily dissolve in the slag. Furtherpurities which have been acquired by the premore, some or the carbon is oxidized thereby vious operation, whereupon the bath is ready 5 The present invention relates to improvements in methods of refining ferro-alloys and alloy steels and has for its principal object the production of ferro-alloys and alloy steels of increased forming carbon monoxide which sweeps through the bath and exerts a beneficial scavenging 'action. A further oxy salt of. barium which is available is barium carbonate. In the use of this for the addition of the nickel ingredient after which the metal may be poured.

In lieu of first purifying the ferro alloy separately, I may use an ordinary unpurified ferro alloy and rely upon the purification treatment in the alloy steel bath to efi'ect the necessary purification. This requires a somewhat more strenuous treatment in which larger quantities of the purifying agent are used, and in such case at least two treatments with the barium mixture are advisable.

It is, of course, immaterial so far as the character of the finished. product is concerned, whether the purification of the ferro alloy is carried out in the same plant simultaneously with the melting of the steellacking the alloy element or whether these operations are performed at different points and the thus previously purified alloy furnished the steel maker. Furthermore, in the manufacture of the purified ferro alloy the treatment with the barium salts will be carried out irrespective of the manner in which the alloy has been produced, i. e., whether directly from the ore or not.

- It has been found that the barium salts hasten the melting of the steel, and I therefore prefer to add the treating agent to the carbon steel, for example, before the melting is completed. The final treatment with the barium salts'may take place either in the furnace or in the ladle.

Among the advantages resulting from my improvement may be mentioned the following: A1- loy steels produced in accordance with my invention have demonstrated superior physical properties as a result of the cleaner metal which has been produced. Not only are the physical impurities, such as carbides, nitrides and dissolved slag, eliminated from the metal but dissolved gases are eliminated from the bath to a substantial degree whereby ingots are produced which are free from pipes and blow holes. Since fewer impurities are in the bath to start with, and since such as are present in the bath are more quickly removed, the period of heat is greatly reduced with consequent saving of cost. Moreover, because of the shorter time of heating, much less of the alloying element, as for example, chromium, is lost from the bath whereby the composition of the poured metal can be gaged with sufilcient accuracy from the known composition and amount of the ingredients added to the bath, and the necessity eliminated for analyses of the metal during the heat which latter in such a case must be held until a report can be had on such analyses.

While I have described in detail the manufacture of a chrome nickel steel in accordance with my invention, it will be understood that themanufacture of other alloy steels as'molybdenum, vanadium, manganese, tungsten, and

others will be carried .out similarly. I also wish it understood that the specific proportions given of the ingredients of the treating agent may be varied considerably to suit different starting materials and to alter the effects of the treatment somewhat. Thus, by increasing the amount of barium peroxide, a decrease in the amount of carbon in the steel is brought about through the oxidizing effect of the excess oxygen upon the carbon.

I claim:

1. The process of making alloy steel which consists in adding to the steel in molten condition a mixture composed substantially of barium peroxide and barium carbonate, the amount of barium peroxide being substantially in excess of the amount of barium carbonate.

2. The process of making alloy steel which consists in adding to the steel in molten condition a mixture composed substantially ofbarium peroxide and barium carbonate in the proportion of approximately three parts of the former to one part of the latter.

3. The process of making stainless chrome steel which consists in adding to the molten bath a mixture comprised essentially of barium peroxide and barium carbonate, the amount of barium peroxide being substantially in excess of the amount of barium carbonate.

4. The process of making stainless chrome steel which consists in adding to the molten bath, shortly before pouring, a mixture comprised essentially of barium peroxide and barium carbonate, the amount of barium peroxide being substantially in excess of the amount of barium carbonate.

5. The process of refining stainless chrome steel which consists in adding to the steel in the ladle shortly before pouring a mixture comprising essentially barium peroxide and barium carbonate, the amount of barium peroxide being substantially in excess of the amount of barium bining said baths, the steps which consist in treating both said baths with a mixture comprising essentially barium carbonate and barium peroxide.

8. The process according to the preceding claim including also the step of treating the final bath with said mixture of barium carbonate and bariun'i peroxide.

BEN F. HARDESTY. 

